<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        ul{
            width: 100%;
            height: 100px;
            color: red;
        }
        li{
            float: left;
        }
        ul::after{
            content: "";
            display: table;
            clear: both;
        }
    </style>
</head>
<body>
    <ul>
        <li>html</li>
        <li>html</li>
        <li>html</li>
    </ul>
</body>
</html>